I have got the book yesterday from Amazon Germany. Not being a Slipper specialist, my first impression is, that there are a lot of new information for me inside; for my (personal) taste perhaps a too extensive part about complex hybrids!
Complex hybrids are quite a fascinating field. So far I know of only a couple of books ( including the Koopowitz and Hasegawa "Novelty Slipper Orchids" that deals with hybrids. It is a pity, because there is a lot to say and to study about those. That's a very good point for Harold book actually, but it could have been more extensive ( or maybe another book). Do not believe the breeders travel in the greenhouses and think 'one white boum another white, that's it, the next FCC is on the way !'. There are a lot of plants that have been studied, and are well known for their traits. From niveum to Hellas to many others. But no book, absolutely none, informs about that.
Personnally, I am a bit tired with the paph species book. After a while, one knows what is a delenatii or an armeniacum. For the remaining, there are a couple problematic groups for the taxonomy, in the insigne/coccineum/helenae/barbigerum/rhizomatosum and the like, but nearly no book focus on these extensively anyway.
They are passed by with a couple of nice photos of "typical" helenae ( who knows that the common type of helenae is dirty brown, not yellow?), barbigerum ( the dull, widely available type, there are some populations that have bright, clear, colors), and that's it.
There is no need to repeat again and again what a rothschildianum or a delenatii is, everyone knows, and there are a lot of books that already mentions those two species.
One thing that always surprise me with all the paphs species books, there are quite a few plants that are known for ages, and never mentioned.
What about Paph praestans(glanduliferum) 'red leaf', with burgundy underside of the leaves ? It is quite to very common, but nowhere to be found in the "paph taxonomy books", where praestans has "green leaves".
Kolopakingii and topperii are quite different plants and flowers. There are not that good explanations, yet all the authors have mentionned the two.
Palawanense is NOT the dwarf paph philippinense, but a hybrid between randsii x philippinense, very rare.
Sanderianum can be as large as kolopakingii, but no mention in any taxonomy books.
In the natural hybrids, argus, acmodontum and ciliolare breed like rabbits. There are giant forms of ciliolare. Never mentioned in those books.
P.rothschildianum has a pygmy form. No mention, nowhere, except in 'Novelty Slipper Orchids'. The plants are in the 20-25cm leafspan (not individual leaf, leafspan) maximum. All the taxonomists have seen plants of that.
For dianthum and parishii, I believed before that they were separate species. Now, I would think that dianthum is a variety of parishii, because many plants from Laos are intermediate between the two. Yet, the paph books will show pictures of "typical" parishii, and "typical" dianthum, not the intermediate forms that are much more interesting.
And I have to know first hand that all the authors are aware of the above mentionned plants, and have seen them. Lance Birk actually introduced some pictures of funny plants, like a gorgeous lowii/haynaldianum from Philippines. But for the remaining, it is always the pictures of typical examples of typical species. The pictorial indexes 'Paphiopedilum in Taiwan' are wonderful, to know how good a plant can be (even if there are some dogs in their pics, like some micranthum or hangianum, but anyway), but many plants available will not fit these pictures at all.
For the taxonomy, I remember that it is possible to keep a name that is popular, not to make any confusion. I belive crossii is the older name for callosum, but it would make a real mess. Think in 20 years, people have to still remember thailandense, callosum var. vietnamense ( not formally described, but appears here and there), sublaeve, viniferum, crossii, and some more. Lumping is maybe good for taxonomists, but for horticulturists, it is a real disaster. Many 'varieties' name are essential to understand why an hybrid or a plant looks like that. Callosum var. thailandense is maybe a callosum ( for sure), close to sublaeve botanically, but for breeding, the results are different. wilhelminiae is 10-12 cm leafspan, gardineri 20-30 cm, and praestans from Waigeo can be 1.2m leafspan. If we lump everything under wilhelminiae and praestans, in a century, people will not be able to remake some crosses.
The best paph book remains to be written I believe...